1. Technical Field
The present disclosure relates to an imaging device such as a camera and an analyzing apparatus using the imaging device.
2. Description of the Related Art
There is a growing need for an imaging device that not only acquires a color image, but also has other functions. In particular, recently, there has been an increase in research and development in the field of spectroscopic imaging that performs image acquisition for each of a plurality of wavelengths.
In spectroscopic imaging, by acquiring two-dimensional brightness information of an object for a plurality of wavelengths or wavelength bands, it is possible to sense useful information that is difficult or impossible to sense only by visual inspection of the object. These information includes, for example, the degree of freshness or the sugar content of vegetables or fruits, extraction of a foreign body in various product inspection lines, and identification of diseased tissue by analysis of fluorescence that is generated as a result of an object being irradiated with excitation light.
There are mainly two methods for performing spectroscopic imaging, One is a method by which a plurality of illumination light sources, each having a specific wavelength, are prepared and an object is illuminated thereby with switching being performed between the illumination light sources and, at the same time, images of the object are taken by an imaging device at emission of each illumination light source. The other is a method by which an object is illuminated by a light source, such as a white light source, which has a wide wavelength band and an image thereof is acquired by an imaging device via a spectral filter that allows only a desired wavelength to pass therethrough.
A suitable method of the above-described two methods is selected depending on an object to be measured or an environment and circumstances in which measurement is performed. The latter has the advantage that the flexibility for the number of wavelengths or the wavelength bandwidth that can be acquired is high and spectroscopic imaging can be performed relatively easily. As a specific example, a filter wheel provided with a plurality of spectral filters having different transmission wavelength bands is positioned in front of an imaging device and switching between the spectral filters is performed, whereby a plurality of images having different wavelength bands can be sequentially acquired.
U.S. Pat. No. 7,433,042 and Japanese Unexamined Parent Application Publication No. 2011-75562 disclose examples in which a plurality of wavelength images are acquired at the same time by one imaging device.